摘要
针对可见光通信(VLC)正交频分复用(OFDM)系统发光二极管(LED)动态范围窄、非线性和限幅失真严重等问题,利用光源具有多个灯芯的特点,将OFDM频带划分为多个子带,每个子带内数据通过傅里叶反变换(IFFT)产生一路独立信号输入LED灯芯,所有LED灯芯发出的光信号在空间上叠加形成光叠加OFDM(OSM-OFDM)信号。在相同直流偏置情况下,OSM-OFDM系统每一路信号的调制深度较低,能够有效地避免LED非线性和限幅影响,特别是在输入信号功率较大时,系统误码率(BER)降低了至少1个数量级。根据有效信噪比(SNR)最大原则能够得到OSM-OFDM系统最优直流偏置,而且在系统设计时可以根据系统有效信噪比公式选择合适的LED灯芯数。实验表明,OSM-OFDM系统BER性能要比直流偏置光OFDM(DCO-OFDM)系统提升了1个数量级。
The light emitting diode （LED） has limited dynamic range, significant nonlinearity and clipping distortion in visible light communication orthogonal frequency division multiplexing （OFDM） system. By using the characteristics of light source which has many wicks, the bandwidth of OFDM is divided into several sub-bands. Data from each sub-band is used to generate a single signal by the inverse fast Fourier transform （IFFT） and the single signal is input into each LED wick. Then the optical superposition modulation OFDM （OSM-OFDM） signal is formed by the superposition of optical signals from all the LED wicks. The modulation index of every single signal is low with the same DC bias in OSM-OFDM system. So it effectively avoids the nonlinearity and clipping distortion caused by LED. In particular, the system bit error rate （BER） performance decreases at least by an order of magnitude with high input power. The optimal DC bias of OSM-OFDM system is achieved by the principle of maximum effective signal to noise ratio （SNR）. And the suitable number of LED wicks is chosen based on the equation of effective SNR when a real system is designed. Experimental results show that the BER performance of OSM- OFDM system has improved an order of magnitude than the direct current optical orthogonal frequency division multiplexing （ECO-OFDM） system.
出处
《光电子．激光》
EI
CAS
CSCD
北大核心
2015年第6期1087-1093,共7页
Journal of Optoelectronics·Laser
基金
国家自然科学基金(61271253)
国家"863计划"(2013AA013603)资助项目
